feat: analysis providers, settings UI, song search, WAV duration fix

- Multi-provider AI analysis (Anthropic, OpenAI, Ollama, Algorithmic)
- server-only guards on all provider files; client bundle fix
- /settings page with provider status, Ollama model picker, preferences
- Song search box on /analyze replacing raw MBID input (debounced, keyboard nav)
- Auto-register song via MusicBrainz on POST /api/tracks (no more 404)
- Fix WAV duration bug: last section songEnd was double-counting elapsed time
- Registry sync comment updated for self-hosted HTTPS git servers

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/api/analyze/providers/route.ts

@@ -0,0 +1,20 @@
+import { NextResponse } from "next/server";
+import { getProviderInfoList, getOllamaModels } from "@/lib/analysis/providers/registry";
+
+/**
+ * GET /api/analyze/providers
+ *
+ * Returns all providers (available and unavailable) and the list of
+ * locally available Ollama models (empty array if Ollama is unreachable).
+ */
+export async function GET() {
+  const [providers, ollamaModels] = await Promise.all([
+    getProviderInfoList(),
+    getOllamaModels(),
+  ]);
+
+  return NextResponse.json(
+    { providers, ollamaModels },
+    { headers: { "Cache-Control": "no-store" } }
+  );
+}